Methods and tools for femoral resection in knee surgery

ABSTRACT

Tools for resecting the femur include an anchoring device, a three-way alignment guide and a six way alignment guide attachable to the anchoring device, a resection guide attachable to the three-way alignment guide and equipped with couplings for trackers, an A-P sizer, a femoral sizing block bushing attachable to the six-way alignment guide, a 4-in-1 femoral cutting block, a 5-in-1 positional alignment guide attachable to the six-way alignment guide, a pair of diodes, and a 5-in-one cutting block. Methods of utilizing the apparatus are also disclosed

[0001] This application is related to patent application Ser. No.09/811,272, filed Mar. 17, 2001, entitled “Tools Used In PerformingFemoral And Tibial Resection In Knee Surgery”; patent application Ser.No. 09/811,043, filed Mar. 17, 2001, entitled “Methods Used InPerforming Femoral And Tibial Resection In Knee Surgery”; patentapplication Ser. No. 09/811,042, filed Mar. 17, 2001, entitled “SystemsUsed In Performing Femoral And Tibial Resection In Knee Surgery”; patentapplication Ser. No. 09/811,318, filed Mar. 17, 2001, entitled“Apparatus Used In Performing Femoral And Tibial Resection In KneeSurgery” and patent application Ser. No. 09/746,800 filed Dec. 23, 2000,entitled “Methods and Tools For Femoral Resection In Primary KneeSurgery”, the complete disclosures of which are hereby incorporated byreference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to methods and tools used in kneearthroplasty. More particularly, the invention relates to methods andtools used in knee surgery where artificial femoral and tibialcomponents are installed.

[0004] 2. Brief Description Of The Prior Art

[0005] Total knee arthroplasty involves the replacement of portions ofthe patellar, femur and tibia with artificial components. In particular,a proximal portion of the tibia and a distal portion of the femur arecut away (resected) and replaced with artificial components.

[0006] As used herein, when referring to bones or other body parts, theterm “proximal” means closest to the heart and the term “distal” meansmore distant from the heart. When referring to tools and instruments,the term “proximal” means closest to the practitioner and the term“distal” means distant from the practitioner.

[0007] There are several types of knee prostheses known in the art. Onetype is sometimes referred to as a “resurfacing type”. In theseprostheses, the articular surface of the distal femur and proximal tibiaare “resurfaced” with respective metal and plastic condylar-typearticular bearing components.

[0008] The femoral component is a metallic alloy construction(cobalt-chrome alloy or 6A14V titanium alloy) and provides medial andlateral condylar bearing surfaces of multi-radius design of similarshape and geometry as the natural distal femur or femoral-side of theknee joint.

[0009] One important aspect of these procedures is the correct resectionof the distal femur and proximal tibia. These resections must provideplanes which are correctly angled in order to properly accept theprosthetic components. In particular, the resection planes must becorrectly located relative to three parameters: proximal-distallocation, varus-valgus angle, and flexion-extension angle.

[0010] Moreover, following distal resection, the femur must be shapedwith the aid of a cutting block. The cutting block must be correctlylocated relative to internal-external rotation, medial-lateral position,and anterior-posterior position.

[0011] Recently, various computerized systems have been introduced toaid the practitioner during different surgical procedures. A typicalsystem is described in the attached Appendix.

[0012] These systems include multiple video cameras which are deployedabove the surgical site and a plurality of dynamic reference frame (DRF)devices, also known as trackers, which are attached to body parts andsurgical instruments. The trackers are generally LED devices which arevisible to the cameras. Using software designed for a particularsurgical procedure, a computer receiving input from the cameras guidesthe placement of surgical instruments.

[0013] The prior art instruments used for determining the correct planesfor tibial and femoral resection in total knee arthroplasty are not wellsuited for use with computerized systems. The known tools utilize eitherintra-medullary alignment or extra-medullary alignment and adjustment ofthe degrees of freedom simultaneously is difficult or impossible.Moreover, in order to be useful with computer aided navigation systems,trackers must be attached to the tools. Existing tools do not permit theattachment of trackers.

SUMMARY OF THE INVENTION

[0014] It is therefore an object of the invention to provide methods andtools for performing femoral resection.

[0015] It is also an object of the invention to provide methods andtools for femoral resection which allow location of a cutting guiderelative to six parameters.

[0016] It is another object of the invention to provide methods andtools for femoral resection which are infinitely adjustable.

[0017] It is still another object of the invention to provide methodsand tools for femoral resection which are adapted to be used withcomputer aided navigation systems.

[0018] In accord with these objects which will be discussed in detailbelow, the tools according to a first embodiment of the presentinvention include an anchoring device for attachment to the femur and, athree-way alignment guide attachable to the anchoring device andadjustable relative to three parameters, a resection guide attachable tothe alignment guide and equipped with couplings for trackers, anadjustable anterior-posterior sizer, a distal-proximal medial-lateralpositioning guide, a medial-lateral cam lock, an anterior-posteriorpositioning guide, a femoral sizing block bushing, and femoral cuttingguide.

[0019] The tools according to a second embodiment of the presentinvention include an anchoring device for attachment to the femur and, asix-way alignment guide attachable to the anchoring device andadjustable relative to six parameters, a pivotal 5-in-1 positionalalignment jig attachable to the alignment guide and equipped withcouplings for trackers, a pair of mounting diodes attachable to theepicondylar region of the femur, and a 5-in-1 cutting guide mountable onthe diodes.

[0020] A first embodiment of the methods of the invention includesoperating the computer aided navigation apparatus in the conventionalmanner including attaching one or more trackers to the bone to beresected; choosing a location for the anchoring device with or withoutguidance from the computer and installing the anchoring device;attaching the three-way alignment guide to the anchoring device;attaching a resection guide to the alignment guide; attaching one or twotrackers to the resection guide; locating the resection guide with theaid of the alignment guide and the computer; fixing the resection guideto the bone with pins through the rotatable pin guides; and resectingthe bone.

[0021] After the bone is resected, the adjustable anterior-posteriorsizer is used to size the femur.

[0022] Next, the distal-proximal medial-lateral positioning guide,medial-lateral cam lock, anterior-posterior positioning guide, andfemoral sizing block bushing are attached to the alignment guide.

[0023] The distal-proximal medial-lateral positioning guide,medial-lateral cam lock, and anterior-posterior positioning guide, whenattached to the three-way guide, convert the three-way guide into asix-way guide. A tracker is preferably attached to the femoral sizingblock bushing. The position of the bushing is adjusted inproximal-distal, varus-valgus, medial-lateral, and anterior-posteriordirections. Two holes are drilled using the bushing as a guide. Thefemoral cutting guide is attached to the holes and the anterior andposterior cuts and chamfer cuts are made.

[0024] A second embodiment of the methods of the invention includesoperating the computer aided navigation apparatus in the conventionalmanner including attaching one or more trackers to the bone to beresected; choosing a location for the anchoring device with or withoutguidance from the computer and installing the anchoring device;attaching the six-way alignment guide to the anchoring device; attachingthe pivotal 5-in-1 positional alignment jig to the alignment guide;attaching a tracker to the jig; positioning the jig in the varus-valgus,flexion-extension, internal-external rotation, distal-proximal, andanterior-posterior directions; drilling four holes in the epicondylarregion using the jig as a guide; removing the jig, the alignment guide,and the anchoring device; installing a pair of diodes in the epicondylarregion with screws in the holes; and mounting the 5-in-1 cutting guideon the diodes.

[0025] The 5-in-1 cutting guide is then used to perform all of thefemoral cuts as described in previously incorporated application Ser.No. 09/746,800.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a broken perspective view of the distal femur with ananchoring device according to the invention;

[0027]FIG. 2 is a side elevational view of the anchoring deviceinstalled in the distal femur;

[0028]FIG. 3 is a perspective view of the anchoring device installed inthe distal femur with a three-way alignment guide according to theinvention not yet attached to the anchoring device;

[0029]FIG. 4 is a view similar to FIG. 3 showing the alignment guideattached to the anchoring device;

[0030]FIG. 5 is a perspective view showing a first embodiment of aresection guide according to the invention not yet attached to thethree-way alignment guide;

[0031]FIG. 6 is a perspective view showing a first embodiment of aresection guide according to the invention attached to the three-wayalignment guide;

[0032]FIG. 7 is a side elevational view showing a first embodiment of aresection guide according to the invention attached to the three-wayalignment guide;

[0033]FIGS. 8 and 8A are perspective views of an anterior-posteriorsizer;

[0034]FIG. 9 is an exploded perspective view of the distal-proximalmedial-lateral positioning guide, medial-lateral cam lock,anterior-posterior positioning guide, and femoral sizing block bushing;

[0035]FIG. 10 is a plan view of the distal-proximal medial-lateralpositioning guide, medial-lateral cam lock, anterior-posteriorpositioning guide, and femoral sizing block bushing coupled to thealignment guide;

[0036]FIGS. 11 and 12 are perspective views of the distal-proximalmedial-lateral positioning guide, medial-lateral cam lock,anterior-posterior positioning guide, and femoral sizing block bushingcoupled to the alignment guide;

[0037]FIG. 13 is a side elevation view of the distal-proximalmedial-lateral positioning guide, medial-lateral cam lock,anterior-posterior positioning guide, and femoral sizing block bushingcoupled to the alignment guide;

[0038]FIGS. 14 and 15 are perspective views of a femoral cutting guide;

[0039]FIG. 16 is an exploded perspective view of a pivotal 5-in-1positional alignment jig and five-way alignment guide;

[0040] FIGS. 17-19 are perspective views of the pivotal 5-in-1positional alignment jig and five-way alignment guide coupled to theanchoring device;

[0041]FIG. 20 is a perspective view of a pair of diodes coupled to theepicondylar region of the femur; and

[0042]FIG. 21 is a perspective view of a 5-in-one cutting block mountedon the diodes.

BRIEF DESCRIPTION OF THE APPENDIX

[0043] The attached ten page Appendix describes the parts and assemblyof a computer navigation system suitable for use with the invention.

DETAILED DESCRIPTION

[0044] Turning now to the Figures, the apparatus of the invention willbe best understood by a description of the methods of the invention withreference to the Figures. As shown in FIGS. 1 and 2 an anchoring device10 is installed in the bone 1 in a region proximal to the lateralanterior cortex and within the incision. The location for the anchoringdevice may be chosen by eye or with the aid of the tracking/navigationsoftware, with an emphasis on paralleling the anchoring device body tothe sagital plane. As shown in the Figures, the anchoring device 10 is apin which is screwed into the bone. Other anchoring devices such asplates could be used, however.

[0045] With the anchoring device 10 in place, the alignment guide 12 islowered on to it as shown in FIGS. 3-5. As seen best in FIG. 5, thealignment guide 12 has three cam locks 12 a, 12 b, 12 c. The cam lock 12a allows the alignment guide to be adjusted according toflexion-extension angle relative to the anchoring device 10. The camlock 12 b allows the alignment guide to be adjusted according tovarus-valgus angle relative to the anchoring device 10. The cam lock 12c opens the end of the alignment device to receive the resection guide14 shown in FIGS. 5-7 and also allows for distal-proximal adjustment.

[0046] Referring now to FIGS. 5-7, the resection guide 14 has a cuttingguide surface 14 a, an attachment rod 14 b, a pair of connectors 14 c,14 d for connecting trackers (not shown), a pair of rotatable pin guides14 e, 14 f, and a pair of fail safe mounting bores 14 g, 14 h. Theresection guide 14 is attached to the alignment guide 12 by opening camlock 12 c and inserting the attachment rod 14 b into the alignmentguide. It will be appreciated that the cam lock 12 c allowsproximal-distal positioning of the resection guide 14. After theresection guide 14 is attached to the alignment device 12, a tracker isattached to the guide 14.

[0047] With the tracker attached, the first cam lock 12 a is opened andthe resection guide is moved in the varus-valgus plane until thenavigation software indicates the proper alignment. The cam lock 12 a isthen locked. Cam lock 12 b is unlocked and the resection guide is movedin the flexion-extension plane until the navigation software indicatesthe proper alignment. The cam lock 12 b is then locked.

[0048] Lastly, the cam lock 12 c is opened and the resection guide ispositioned in the proximal-distal plane until the navigation softwareindicates the proper alignment. The cam lock 12 c is then locked. Withthe resection guide properly located, it may be affixed to the bone withpins (not shown) via the rotatable pin guides 14 e, 14 f. The pin guidesare rotatable so that the practitioner may choose the best site forinserting a pin. The next step in the procedure is to resect the distalend of the femur using the resection guide 14.

[0049] Those skilled in the art will appreciate that if the anchor pin10 is not substantially parallel to the sagital plane, the steps mayneed to be repeated to tune out error introduced by the misalignedanchor pin. One possible solution is to install the pin with a drillhaving an attached tracker thereby allowing the navigation software toguide the placement of the pin.

[0050] Following distal femoral resection, the femur is sized usingeither of the following methods:

[0051] 1) Conventional sizing using either the Monogram or X-celeratesizing guides is performed. Surface digitization of the posteriorcondyles must be performed by the surgeon using the pointer by runningthe pointer tip over the posterior condylar bone and/or cartilage. Thesizing guide is placed flush on the resected distal femur with theposterior skids against the posterior condyles. Either the sizing stylusor blade runner (or saw blade) is used to measure the most prominentaspect of the femoral lateral cortex. The femoral sizing block bushingcan now be navigated.

[0052] An exemplary sizing guide 15 is shown in FIGS. 8 and 8a. Theadjustable A-P sizer 15 sets internal-external rotation and also allowsan AP movement of +/−2 mm. This instrument is used after the femoraldistal cut is performed. The feet 15 a, 15 b are inserted under theposterior condyles. The jig is allowed to move through six degreeseither internally or externally as shown by the indicia between theletters “L” and “R”.

[0053] A blade runner is introduced into one of the slots (labeled in 3,5, 7, 9, 11, and 13 mm). The slot selected is the one that gives therequired run-out anteriorly. If the surgeon is in between sizes, if hegoes down a size, he will notch the femur, or if he moves up a size hewill leave a gap. The jig allows the surgeon to obtain the optimalposition.

[0054] 2) Alternatively, software algorithms are used to size the femur.Surface digitization of the trochlear groove (patella track) andposterior condyles are performed by the surgeon using the pointer byrunning the pointer tip over the posterior condylar bone and/orcartilage. Digitized data is analyzed in the sagital plane. Directcorrelation to (or matching of) the correct femoral component isachieved via the software coding/algorithms. The surgeon will be able tovisualize the matching on the operating room computer monitor (graphicalinterface). Sizing is complete using solely digitization methods. Thefemoral sizing block bushing can now be navigated.

[0055] Turning now to FIGS. 9-13, after the distal femur is resected andsizing is completed, the appropriately sized femoral sizing blockbushing 16 is attached to the alignment guide 12 using ananterior-posterior positioning guide 18 having a cam lock 18 a, amedial-lateral cam lock 20, and a distal-proximal medial-lateralpositioning guide 22. The bushing 16 has a vertical shaft 16 a, a pairof drill guides 16 b, 16 c, and a tracker coupling 16 d. The verticalshaft 16 a is inserted into the anterior-posterior positioning guide 18which is coupled to the medial-lateral cam lock 20 which is slidablycoupled to the distal-proximal medial-lateral positioning guide 22.

[0056] A tracker (not shown) is coupled to the coupling 16 d. Using thecam locks, the distal-proximal position is set by manually presentingthe bushing 16 to the resected face of the femur. The internal-externalrotation is navigated and the cam lock is locked on the positioningguide. The medial-lateral positioning of the bushing is navigated andlocked using the medial-lateral cam lock 20. Finally, anterior-posteriorpositioning is navigated and locked with the cam lock 18 a. Verificationof the navigated position is done in conjunction with the screens on thecomputer. Once satisfied with the navigated position, two holes aredrilled through the drill guides 16 b, 16 c. The complete anchoringmechanism is removed and the appropriate femoral cutting block isattached.

[0057]FIGS. 14 and 15 illustrate an exemplary cutting block 24. Thecutting block 24 has a pair of pins 24 a, 24 b which are impacted intothe holes drilled with the bushing 16 (described above).

[0058] Additional fixation holes 24 c-24 f are provided for optionalfixation with pins. The cutting guide has four guiding surfaces: theanterior cut guiding surface 24 g, the posterior cut guiding surface 24h, the anterior chamfer cut guiding surface 24 i, and the posteriorchamfer cut guiding surface 24 j. After these four cuts are made, thecutting block is removed and the femur is near ready for accepting theprosthesis.

[0059] A second embodiment of the methods and tools of the invention isillustrated with reference to FIGS. 16 through 21. The second embodimentutilized the same anchoring device 10, alignment guide 12, and thealignment devices 18, 20, 22 with a minor alteration. Theanterior-posterior alignment device 18′ shown in the Figures has its camlock 18′a oriented in a slightly different position than the cam lock 18a on the alignment device 18. According to this embodiment, the devices12, 18′, 20, and 22 are assembled to provide what amounts to a six-wayalignment guide. Further according to this embodiment, a pivotal 5-in-1positional alignment jig is provided which includes the components 26,28, and 30. Component 26 is a T-bar having a vertical shaft 26 a, alateral arm 26 b and a medial arm 26 c. Component 28 is a medialdrilling guide arm having a mounting hole 28 a, a set screw 28 b, anddrill guides 28 c. Component 30 is a lateral drilling guide arm having amounting hole 30 a, a set screw 30 b, and drill guides 30 c.

[0060] After the femur is digitized as described above with reference tothe first embodiment, the components are assembled as shown in FIGS.17-19. A tracker (not shown) is attached to one of the set screws 28 b,30 b.

[0061] Using the various CAM locks, the medial and lateral drillingguides 28, 30 are positioned in the following directions in thefollowing order: varus-valgus, flexion-extension, internal-externalrotation, distal-proximal, and anterior-posterior directions.

[0062] More particularly, the sequential locking of the guide beginswith flexion-extension. The cam lock 12 b is opened and the jig isnavigated until the recommended position is reached. Once reached, theflexion-extension cam lock 12 b is engaged.

[0063] Next, varus-valgus lock 12 a is opened and flexion-extension isnavigated. The jig is navigated until the recommended position isreached. Once attained, the varus-valgus cam lock 12 a is engaged. Next,internal-external rotation is navigated.

[0064] The cam lock 12 c is opened and the jig is navigated until therecommended positions are reached.

[0065] Once attained, the internal-external rotation and distal-proximaltranslation are engaged. Next, anterior-posterior positioning isnavigated. The cam lock 18 a is opened and the jig is navigated untilthe recommended position is reached. Once attained, theanterior-posterior cam lock 18 a is engaged. The medial-lateralpositioning is not performed until the 5-in-1 cutting guide is attachedas described below with reference to FIG. 21.

[0066] After the drilling guides are positioned, four holes are drilledinto the epicondylar region using the drill guides 28 c, 30 c. All ofthe devices are then removed from the femur.

[0067] Referring now to FIG. 21, a pair of diodes 32, 34 are installedin the epicondylar region with screws (not shown), in the holes whichwere drilled in the previous step, using a screwdriver 36.

[0068] Turning now to FIG. 21, a 5-in-1 cutting guide 38 is mounted onthe diodes as described in previously incorporated application Ser. No.09/746,800. Prior to fixing the cutting guide with pins, themedial-lateral position of the guide is fine tuned by the surgeon. The5-in-1 cutting block is then pinned in position and is used to performall of the femoral cuts as described in previously incorporatedapplication Ser. No. 09/746,800.

[0069] There have been described and illustrated herein methods andtools for resection of the distal femur. While particular embodiments ofthe invention have been described, it is not intended that the inventionbe limited thereto, as it is intended that the invention be as broad inscope as the art will allow and that the specification be read likewise.For example, the first two positioning steps may be reversed insequence, provided that the navigation software is suitable modified.Moreover, the clamps on the alignment guides need not be cam locks, butcould be other types of clamps. Although the apparatus has beendescribed as separate pieces (e.g. the anchor, the alignment guide, andthe resection guide), it could be two pieces or a single piece. Ingeneral, the methods and tools of the invention could be used with otherjoints other than the knee. It is believed that the methods and toolscould be used in arthroplasty of the hip, shoulder, elbow, etc.

What is claimed is:
 1. An apparatus for guiding the resection of a boneduring arthroplasty, comprising: (a) anchoring means for anchoring theapparatus to the bone; (b) a drill guide coupled to said anchoringmeans; and (c) alignment means coupled to said anchoring means and saiddrill guide for locating said drill guide relative to the anchoringmeans, said alignment means providing three degrees of freedom.
 2. Anapparatus according to claim 1 wherein said alignment means iscontinuously adjustable.
 3. An apparatus according to claim 1 whereinsaid anchoring means is a pin.
 4. An apparatus according to claim 1wherein said alignment means provides five degrees of freedom.
 5. Anapparatus according to claim 1 wherein said three degrees of freedominclude two rotations and one translation.
 6. An apparatus according toclaim 1 wherein said three degrees of freedom include flexion-extension,varus-valgus, and proximal-distal.
 7. An apparatus according to claim 4wherein said five degrees of freedom include flexion-extension,varus-valgus, proximal-distal, medial-lateral, and anterior-posterior.8. An apparatus according to claim 1 wherein said drill guide includesmeans for attaching a computer navigation tracker.
 9. An apparatusaccording to claim 1 wherein said drill guide includes a pair of armshaving guide holes adapted to guide drilling into the epicondylar regionof a femur.
 10. An apparatus according to claim 9 wherein said drillguide includes a T-shaped component and said arms are adapted to becoupled to said T-shaped component.
 11. An apparatus according to claim9 further comprising a cutting block adapted to be coupled to the holesdrilled in the epicondylar region with the drill guide.
 12. An apparatusaccording to claim 11 wherein said cutting block has five surfaces formaking five different cuts on the distal femur.
 13. An apparatusaccording to claim 11 further comprising a pair of diodes adapted to bemounted in the epicondylar region using the holes drilled with saiddrill guide, wherein said cutting block is adapted to ride over saiddiodes.
 14. An apparatus according to claim 1 wherein said drill guideis adapted to guide the drilling of two holes in the distal femur. 15.An apparatus according to claim 14 further comprising a cutting blockhaving two pins adapted to fit into the holes drilled in the distalfemur using the drill guide.
 16. An apparatus according to claim 15wherein said cutting block has four guiding surfaces for making fourdifferent cuts on the distal femur.
 17. A method of resecting a boneduring arthroplasty, said method comprising the steps of: (a) anchoringa drill guide to the bone; (b) aligning the drill guide relative to thebone in three degrees of freedom; (c) locking the drill guide inposition; and (d) drilling the bone using the drill guide.
 18. A methodaccording to claim 17 wherein said step of aligning includes moving thedrill guide through a continuously adjustable range.
 19. A methodaccording to claim 17 further comprising the steps of: (e) coupling acomputer navigation tracker to the drill guide; and (f) using a computernavigation system to perform the step of aligning.
 20. A methodaccording to claim 17 wherein said step of anchoring includes pinning tothe bone.
 21. A method according to claim 17 wherein said three degreesof freedom include two rotations and one translation.
 22. A methodaccording to claim 17 wherein said three degrees of freedom includeflexion-extension, varus-valgus, and proximal-distal.
 23. A methodaccording to claim 17 wherein said step of aligning includes aligning infive degrees of freedom.
 24. A method according to claim 23 wherein saidfive degrees of freedom include flexion-extension, varus-valgus,proximal-distal, medial-lateral, and anterior-posterior.
 25. A methodaccording to claim 17 wherein said step of drilling includes drillingholes in the epicondylar region.
 26. A method according to claim 25further comprising the step of attaching a cutting block to theepicondylar region.
 27. A method according to claim 26 furthercomprising the step of making five different cuts of the distal femurusing the cutting block.
 28. A method according to claim 17 wherein saidstep of drilling includes drilling two holes in the distal surface ofthe femur.
 29. A method according to claim 28 further comprising thestep of attaching a cutting block to the distal femur using the twoholes drilled therein.
 30. A method according to claim 29 furthercomprising the step of making four different cuts of the distal femurusing the cutting block.
 31. An apparatus for guiding the resection of abone during arthroplasty, comprising: (a) anchoring means for anchoringthe apparatus to the bone; (b) a drill guide coupled to said anchoringmeans; (c) alignment means for locating the drill guide relative to theanchoring means, said alignment means providing three degrees offreedom; and (d) a computer navigation system optically coupled to thedrill guide.
 32. An apparatus according to claim 31 wherein said threedegrees of freedom are infinitely variable.
 33. An apparatus accordingto claim 31 wherein said alignment means provides five degrees offreedom.
 34. An apparatus according to claim 33 wherein said fivedegrees of freedom include flexion-extension, varus-valgus,proximal-distal, medial-lateral, and anterior-posterior.
 35. Anapparatus according to claim 31 wherein said anchoring means is a pin.36. An apparatus according to claim 31 wherein said three degrees offreedom include flexion-extension, varus-valgus, and proximal-distal.37. An apparatus according to claim 31 wherein said three degrees offreedom include two rotations and one translation.
 38. An apparatusaccording to claim 31 wherein said drill guide includes means forattaching a computer navigation tracker.
 39. An apparatus according toclaim 31 further comprising a cutting block adapted to be coupled to thedistal femur using holes drilled with said drill guide.
 40. An apparatusaccording to claim 39 wherein said cutting block has four guidingsurfaces for making four different cuts in the distal femur.
 41. Anapparatus according to claim 39 wherein said cutting block has fiveguiding surfaces for making five different cuts in the distal femur. 42.An apparatus for guiding the resection of a bone during arthroplasty,said apparatus comprising a drill guide bushing defining two spacedapart drill guide holes, said drill guide bushing having an orthogonalstem for coupling to an alignment device and a coupling for coupling atracker to the bushing.
 43. A set of tools for guiding the resection ofa bone during arthroplasty, said set of tools comprising: (a) a drillguide bushing defining two spaced apart drill guide holes, said drillguide bushing having an orthogonal stem for coupling to an alignmentdevice and a coupling for coupling a tracker to the bushing; and (b) analignment device having at least three degrees of freedom, saidalignment device being adapted to couple to said stem and couple to ananchoring device.
 44. A set of tools according to claim 43 wherein saiddrill guide is adapted to guide the drilling of holes in the distalfemur.
 45. A set of tools according to claim 43 wherein said alignmentdevice has five degrees of freedom.
 46. A set of tools according toclaim 43 wherein said drill guide bushing includes a medial drill guidebushing and a lateral drill guide bushing, said medial drill guidebushing defining two spaced apart holes for drilling into the medialepicondylar region, and said lateral drill guide bushing defining twospaced apart holes for drilling into the lateral epicondylar region.